It most commonly occurs in hydrothermal quartz veins, disseminated in some contact- & hydrothermal-metamorphic rocks, and in placer deposits. Where gold has been concentrated, it occurs as wires, dendritic crystals, twisted sheets, octahedral crystals, and variably-shaped nuggets. Gold is very rare in crustal rocks - it averages about 5 ppb (parts per billion). Almost all other metals are silvery-colored. Gold is the only metal that has a deep, rich, metallic yellow color. Gold (Au) is the most prestigious metal known, but it's not the most valuable. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals. To find a native element in nature, it must be relatively non-reactive and there must be some concentration process.
Only some elements occur in their native elemental state as minerals. Most of these occur in rocks & minerals, although some occur in very small, trace amounts. Of these, 98 occur naturally on Earth (hydrogen to californium). Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.Įlements are fundamental substances of matter - matter that is composed of the same types of atoms. Mineral classification is based on anion chemistry. Currently, there are over 5700 named and described minerals - about 200 of them are common and about 20 of them are very common. At its simplest, a mineral is a naturally-occurring solid chemical. (public display, Field Museum of Natural History, Chicago, Illinois, USA)Ī mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties.
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